Audio watermarking is the process of embedding information items (called watermark) into an audio signal in an inaudible manner.
An original audio signal co can be considered as representing a channel for conveying watermark information m using a key k. In turn, watermarking can be modelled as a form of communication. There exist different ways of how to incorporate the original signal co into the communication model. In a basic model the original signal co is considered as a noise signal. The information about the host signal is not exploited in the modulation step. In advanced models the original audio signal is examined in the watermark encoder before adding a corresponding watermark signal w. This kind of processing is usually referred to as “watermarking with informed embedding” or simply “informed embedding”. In such case the watermark signal w is shaped according to a perceptual model and is then applied to the host signal in the modulation step.